Tape drives store a vast amount of digital information on rolls of magnetic tape and are often used to backup information stored in computer systems. In a typical drive, magnetic tape is stored on a supply reel contained in a removable cartridge. During read and write operations, the tape is passed at a very high speed along a series of guides that define a tape path to a take up reel in the drive. The tape passes in close proximity to an assembly of read heads and write heads that must be precisely positioned over the desired tracks so data can be accurately read or written.
As magnetic tape is wound onto a tape reel at high speed, the tape entrains air which allows the tape to float over the tape pack. As the tape floats, it drifts to the sides of the reel until the tape finally settles against the top or bottom flange of the reel. The reel flanges are relatively far away from the edge of the free length of tape to prevent the tape from contacting the reel as the tape is winding. If the free length of tape contacts the reel flanges, the impact will cause the tape to abruptly move laterally and disrupt registration between the read/write head and the data track location. Because of the clearance needed to avoid contact with the reel flanges while winding onto the reel, the tape pack ends up being misaligned in height from the tape guides. As the tape is then pulled from that reel, the misalignment of the tape pack with the tape guides can create excessive stress on the edges of the tape. This misalignment also creates disturbances from the guide flanges to the tape and causes track misregistration.